Accelerated flight training like ATP may be making things worse, as in trying to get it all done in a few days, before your body can really adapt.
I would also say try to improve your fitness, make sure you are active, make sure you are well hydrated. Don't over-eat, but make sure you have eaten enough. Make sure you are doing something for exercise. These things affect everyone differently, but you want to make sure as much as possible is on your side.
One thing I notice when doing initial flight training is that many instructors don't really focus the student's attention "outside", and by that, I mean some sort of structure in setting attitudes. The "outside" is the attitude indicator, but if you don't use it properly, you still don't have a good idea what attitude you are in. For this reason, I used to give my students "tunnel vision" at first, they can only look straight ahead, using a consistent seat height for a consistent distance for the horizon to the glareshield/cowling. Then they were taught how to fly at speeds and bank angles based on this attitude indicator, only looking straight ahead, with references drawn with dry erase markers or such, kind of like a "heads up" display. Once they could maintain basic attitudes during turns, climbs, decent, etc., then I'd have them start looking left and right, but the critical aspect that was for ANY CHANGE, they had to use the "attitude indicator" to make that change, so set bank and pitch by looking forward, verify it's holding, then look somewhere else. All too often I got in planes and people would set pitch and bank and be looking elsewhere and nowhere at the same time and they'd simply be all over the place, which doesn't help if you want your brain's perception of what's going on to match what is really going on. This "scan" is basically the same as an instrument scan, just using the outside, but again, all too often this is presented with no structure and pilot's have no real idea of their pitch and/or bank. This is why you get people dropping or raising the nose significantly during turns, etc. You can't see what you can't see.